Concrete for Deck Post Footings
Deck posts support substantial loads from the deck structure, furniture, and occupants. They also often support bearer ends and may be exposed to moisture at ground level. Proper footings ensure structural integrity and meet Australian building code requirements.
Standard Deck Post Footing Dimensions
For typical residential decks, 100mm posts in 300mm diameter holes at 600mm depth provide adequate support. Higher decks, larger spans, or heavy loads require engineering assessment for specific footing specifications. Your deck plans should specify footing requirements.
Concrete Requirements for Four Posts
Four footings at these dimensions require approximately 0.20 cubic metres of concrete including wastage. This translates to roughly 22 bags of 20kg premix concrete, a manageable quantity for DIY mixing. Standard concrete rather than quick-set is preferred for structural footings.
Stirrup and Bracket Installation
Most deck designs use steel stirrups set into the concrete footing rather than timber posts sitting directly in concrete. This keeps timber above ground level, dramatically extending post life. Set stirrup brackets into wet concrete at precise positions matching your deck framing layout.
Level and Alignment Critical
Deck posts must be precisely positioned for bearer and joist framing to work correctly. Set out positions using string lines and verify measurements multiple times before pouring concrete. Stirrup brackets set in wrong positions cannot be adjusted, requiring footing replacement.
Height Considerations
Unlike fence posts set to final height during concreting, deck posts are typically cut to height after bearers are positioned. Allow extra length for adjustment. The stirrup bracket establishes the bottom of the post; final height comes from the deck frame design.
Approval and Inspection
Most Australian jurisdictions require building approval for decks exceeding certain heights or sizes. Footings may require inspection before concrete placement and again before framing proceeds. Understand inspection timing to avoid delays or required rectification.
Need Different Specifications?
Use our post hole calculator to enter your exact hole dimensions and post size. You can also explore our slab calculator or footing calculator for other concrete projects.